1. Field of the Invention
The present invention relates to an audio amplifier and a related voltage supply circuit, and more particularly, to an audio amplifier driven by a single voltage source and a related voltage supply circuit.
2. Description of the Prior Art
Current audio amplifiers are popularly implemented with Class D amplifiers. A conventional Class AB amplifier generates linear signals whereas a Class D amplifier generates pulse width modulation (PWM) signals, which primarily includes audio signals, pulse width modulation signals, and harmonic waves. While a Class D amplifier operates, an output stage metal oxide semiconductor field-effect transistor (MOSFET) of said Class D amplifier is required to be biased with a pair of voltage sources, one of which is a positive voltage source whereas the other one is a negative voltage source, where said pair of voltage sources is mutually opposite in views of electrical pole and is equivalent in aspects of electrical level, for driving said Class D amplifier. In the prior art, the positive voltage source from the pair of voltage sources is coupled to a positive bias terminal of the output stage MOSFET of the Class D amplifier, whereas the negative voltage source from said pair of voltage sources is coupled to a negative bias terminal of the output stage MOSFET of said Class D amplifier, for biasing said Class D amplifier. That is, a port has to be further added on each of the positive bias terminal and the negative bias terminal of the output stage MOSFET of the Class D amplifier for receiving the positive voltage source and the negative voltage source respectively, and for driving the Class D amplifier.